The invention relates to a fiber-optical beam splitting device for the coupling in or out of light into or out of an optical fiber from or into different directions of the environment of the optical fiber.
For the branching of light guided in an optical fiber or for coupling light from different directions into the optical fiber, different measures are known, such as fusion couplers or the use of partially reflecting mirrors which all have the disadvantage that, in comparison to the fiber diameter, they take up a relatively large volume and require relatively expensive manufacturing methods.
It is therefore an object of the invention to provide a fiber-optical beam splitting device which has a very compact and simple construction and the splitting relationship of which can be adjusted. This object is achieved according to preferred embodiments of the invention by a beam splitting device for the coupling in or out of light into or out of an optical fiber from or into different directions of the environment of the optical fiber, characterized in that at least one front face of the optical fiber is constructed in the shape of a prism, the angle Y between the longitudinal axis of the fiber and a surface of the prism following the condition wherein ##EQU1## in which equation
n.sub.1 =the refraction index of the fiber core,
n.sub.2 =the refraction index of the fiber sheath,
n.sub.3 =the refraction index of the medium surrounding the optical fiber.
Although light wave wave guides with sloping front faces are known per se (for example, German Published Examined patent application DE-AS 21 31 500), such measures are used only for changing the aperture angle. In contrast, the device according to the invention provides a fiber-optical beam splitting device which either radiates the light emerging from the fiber in different directions of the environment or can receive light from these directions. In order to make this possible, the angle between the longitudinal axis of the fiber and a surface of the end face of the optical fiber, which may be ground, for example, in the shape of a ridge prism, must not fall below certain limits or exceed certain limits. If this angle .gamma. assumes the value indicated by the equation ##EQU2## a T-shaped branching with right angles between the individual beaming direction is even possible which allows a particularly simple construction of this type of a beam splitting device.
The beam splitting device may be used for various purposes, in which case particularly the uses in an optoelectrical transmitting and receiving device or as a fiberoptical coupler are very advantageous.
Basically, the invention is not restricted to front faces of the optical fiber constructed with two surfaces, so that a splitting into more than only two beam directions is possible.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.